Re: Best way to enlarge a DXF drawing for cutting tool paths?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mark Roberts" <mark@f...>
wrote:

> Hi All:
> Regarding cutting wooden parts on a HobbyCNC 3 axis mill:
>
> What is the best way to enlarge a part on a DXF file to compensate

for

> the tool width? I have parts for an airplane I wish to cut. In

ModelCAD

> (or any other drawing program) if I select the part and use

the "scale"

> option, and I scale the selected part by 1/2 the bit size (i.e.: I

scale

> the part up 0.015625 -- 1/2 of the 1/32 inch cutting tool--), I get

an

> uneven result. The length and width scaled do not even come close

to the

> 0.015625 outline I am trying to achieve. All I want to do is get a
> 0.015625 outline of the part I am wanting to cut, and put that

outline

> on a different layer so as to use that layer for the tool path.
>
> Any suggestions? What do you all do to compensate for the tool size?
>
> Thanks for helping a newbie!
>
> Mark

Scaling scales everything - like blowing up a balloon. What you want
is to either use a controller that has built in tool offset (take a
look at MACH1). If you want to do it manually import the DXF into
CORELDraw, select an object and click on the "Contour" button. It
will draw another vector object offset or inset from the first. You
have to do it object by object and you can define the offset/inset.
You can then export it back out as a DXF. Several of the CAM
packages out there have definable tool offset as well. Most good CAM
programs allow you to import the DXF, define a tool, define the type
of cut, number of passes, etc and it automatically calculates offset
and step over for that tool. The only reason I mention Corel is that
it is really cheap for older versions and it has some pretty neat
things you can do with objects that CAD systems don't have. Most of
my work is not "pure" machining and falls into the area of decorative
or artistic endevers (heresy on this list!) so I depend a lot on more
graphic intensive packages like Corel and Illustrator to do a lot of
my work. I also use Corel a lot as a file translator since it will
import and export most of the 2D vector and bitmap formats.